Professional video cameras are at the present time cameras which transmit a maximum of video information to a control room so as to obtain the best possible image quality. In a television studio, cameras use wire links of triaxial type. The wire link is however not the most suitable for mobile cameras. To be able to ensure the mobility of a cameraman in a studio or in a stadium, it is necessary to resort to one or more operators whose job is to untangle the cables.
For certain retransmissions of sports events, it is known to resort to wireless cameras. Cameras used at the present time use single-carrier type transmission which requires continuous aiming of the camera with the aid of a directional antenna, as is represented in FIG. 1.
FIG. 1 represents a system for wireless transmission between a camera and a control room according to the state of the art. A camera 1 is fitted with a single-carrier type HF transmitter which transmits the video signal via an antenna 2 placed for example on top of the camera 1. Given the considerable information bit rate (of the order of 50 Mbs compressed) the frequency of transmission is of the order of a gigahertz. Such a frequency range is, however, very sensitive to interference and in particular to echoes.
The use of a directional antenna 3 for reception, for example of parabolic type, makes it possible to circumvent the problems of echoes and ensures good amplification on reception. Since cameras intended for wireless use are chiefly mobile cameras, it is necessary to fit the directional antenna with means permitting a change of orientation and with a handle 4 enabling an operator to change his orientation. The orientation of the directional antenna is achieved either by guesswork, or with the aid of a sight.
Although such a system makes it possible to use a single operator to “accompany” the movements of the camera, this poses problems of lack of attentiveness. The operator must remain attentive throughout the duration of the shot, the duration possibly being very long and the camera movements possibly being unpredictable.